


Who Among Us Is Truly Good?

by Behemoth_King



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Accidental Transformation, Animal Transformation, Dubious Consent, F/F, Hurt/Comfort, Linhardt being a lil shit, Magic, They're in a war fam, Which is why they have Linhardt, ain't no time for stupid feelings, i need edeleth petplay, illegal I say!, it is illegal for Tara Platt to say "good girl" and it not being aimed at Byleth, needed to get this out of my head, no beta we die like the useless lesbians we are, nothing happens while she's in dog form, platonic doggie cuddles, totally normal reaction to shapeshifting
Language: English
Status: Completed
Published: 2019-08-31
Updated: 2019-09-01
Packaged: 2020-10-04 05:38:21
Rating: Not Rated
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,893
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20465906
Author URL: https://archiveofourown.org/users/Behemoth_King/pseuds/Behemoth_King
Summary: Local magic/science geek seeks a better way to stay up by the use of spellcrafting. Only, he needs a brave volunteer to help fine-tune it.Or, Byleth gets turned into a dog for a day. Stuff happens.





	1. Part 1 White Clouds

"Professor, do you have a moment?" Linhardt's voice floated softly from behind you, no doubt him trying not to yawn rather than respecting the library's ironclad rules.

"These books can wait. What do you need?" Byleth turned to give him her attention, putting a tab in her place before putting it back with it's siblings. Having the charge of a whole troop of students rather than fellow mercenaries was a quite a change, but a welcome one. Food and bedding were of living quality for once, and the boss actually talks to her now.

"Well...I need your courage. I have created a new faith spell that I need to try out, but everyone is too afraid to let me test it on them. I had hoped you would have no such reservations." The noble smiled slightly as he spoke, and Byleth knew that signaled potentially bad news but she was still curious. Magic had always interested her, but Jeralt having done his best to not let her learn any for herself. So she wouldn't neglect her other skills, he would say.

But...being as she was their teacher now, she did need to know more about magic of all sorts. Otherwise, how could her students take her lessons seriously?

"A new spell? That's impressive, Linhardt." She hoped her praise sounded ernest despite her stonewall delivery. A common complaint Jeralt would get from their compatriots.

"But unless it fulfills its intended purpose then my time was for nothing. To think I could of slept for a whole month instead...doesn't exactly motivate me to develop my skills further. Wouldn't you agree, professor?"

Clever boy. Byleth saw what he was doing, and decided against her better judgement to allow him to test his new creation on her. "Actually, I have been meaning to learn more about magic. The archbishop has agreed to help me, but I believe being on the receiving end is also important for learning."

She almost fell out of her chair at Linhardt's reaction. He slammed his hand down on the table she was at, with a look that seems similar to what Jeralt has called excitement.

"Let's go to the training arena before I pass out again." Byleth doesn't understand how he could in this state, but decided against bringing it up.

\---

Having found a nice corner away from the prying eyes of others, Linhardt pointed to a spot on the floor. "I just need you to stand still right there."

"Wouldn't it be more effective to tell me what effect you are hoping for? Considering you made the spell for a purpose. Even if it's not exact, I could let you know if you're close to your desired effect." She felt a strange tingle in her skin that seemed to energize her, but knew it had nothing to do with magic.

"Ah my apologizes professor. What I am hoping that my spell will do is actually very hard to pinpoint. To give the receiver energy, make them more managable if they are unruly, make them unruly instead is also an option—"

"Is that even safe?" Byleth furrowed her brows in worry.

"Hence the sigil I put in the place you will be standing." He pointed at the spot again, and Byleth could see the lines marked into the stone's surface.

"Ah of course, you are very well prepared as always."

"I don't plan on underestimating what potential horrors new magic can cause. I hope your resolve is still strong professor?"

"Yes."

"Good, now as I was saying...oh right, its effects. I mostly hope for the energizing effect. Seteth has been making my daily naps in the library difficult, so I thought to find a way to nip the problem in the bud as it were."

"I would figure you to simply find a new spot to nap at." Byleth felt the corners of her mouth curl up slightly.

"I tried." Linhardt sighed very deepy. "The framework for the spell means the effects will wear off shortly, half a minute. So you don't have to worry about permanent changes."

They curled up even more, and she stepped onto the sigil.

Byleth nodded once at the mage protegy, letting him know she was ready.

The telltale signs of magic surrounded his hands and she felt warmth envelope her.

\---

"No! Nononono! I meant for it to be mental changes, not physical!" Linhardt was on his knees panicking, albeit quietly. Byleth tried to talk and ask him what he meant by physical changes.

The sudden sound of a whine coming out of her mouth scared her. Then she realized that her tongue was a lot longer, as was her mouth...was that a muzzle? "The archbishop is going to kill me if this doesn't wear off." Linhardt spoke, and she now realized that she was much shorter than him compared to before he cast the spell.

He finally turned to look at her. "Uh, I don't know if you can understand me professor, but you are currently a dog."

She turned her head to look at herself. The dark fur and shape of a nonhuman creature greeted her eyes.

"You don't seem to be aggressive so I guess you can wander around until the spell wears off." He deactivated the sigil's power, and she saw him hover his hand over her now apparently dog head. Byleth felt her ears go backwards and lips curl up, this time the feeling not positive.

"Sorry professor. You're actually kinda adorable like this. I tried to resist it." Linhardt winced apologetically. 

She huffed and tried to walk around, but having to use four legs instead of two. It wasn't as difficult as she expected, due to growing up on Jeralt's horse.

"Motor skills seem fine, and I am guessing you can understand me?"

She stopped to look at him and forced a nod, the action very unnatural to do in this form.

"Thank the goddess. I'll try to come up with some excuse if people look for you. Just try not to get in any trouble. It should still wear off even though it been over a few min—."

A glint caught her attention and she took off.

"Aaaaaand she's gone....I need a nap."

\---

Smells and colors were different now. As was the way people saw her. While anyone that came close to her head got a slight huff as a warning, that didn't stop them from patting her back. Apparently being a dog gave her more leeway with personal boundries.

Byleth then heard a familiar sound. Her suspicions confirmed when she looked in the direction of its source. Jeralt was with Alois at the marketplace, the look of embarassment covering the white armored man's face.

Making her way between soldiers and civilians, she finally made her way to Jeralt. Plopping down in front of him, she tried to replicate as best she could in the form of a dog, her battle ready stance. Her head held high, ears erect, and paws in line with one another.

"Captain! It's not funny! I was worried I had ru—oh ho look what we got here. I bet this beast smells that game from Dagda you bought for Byleth." Alois bent down, his intent clear.

Jeralt stopped his hand, and Byleth almost wanted to bark with joy. Almost. But Jeralt was here, and she had to look professional.

"You don't hug a stranger any more than you pet a stray on it's head. You can lose a hand like that." Jeralt didn't look fazed.

"Are you sure it's a stray? Seems very well fed to me, maybe a bit too well." Byleth growled at him, but didn't budge otherwise. Alois jumped up a bit.

"It's the fur, she's got a good coat on her. Color reminds me of Byleth's hair actually. Better get these in the box, come on Alois." Jeralt still didn't look fazed he and Alois started to walk away from her, but she began following them, flanking Jeralt's right side just like always.

She soon felt a familiar rough and calloused hand on her head, and her tail started moving on its own.

\---

After leaving Jeralt's room, head throughly patted by passerbys which she has quickly become accustomed to, she hears a familiar voice heading in the direction of the library.

Following it, she notices the position of the sun. Linhardt had enlisted her help around noon and now it seemed a hour or so until evening sets.

More headpats came to her, and it felt very good. For some reason, a dog loose in the church's halls is not a major concern and she is able to make her way to the library, the place where this technically all began.

\---

"—good girl—"

Her ears perked up at those words, drowning out everything else. The speaker was....A good girl? Who was a good girl? Could any girl truly be good? Wait...what was happening to her?

"I had thought most of you had learned your lesson." The calm and soothing voice, though it now had traces of annoyance, of Seteth came up behind her. The man looked at her with a bored look of said annoyance and he grabbed her by the scruff of her neck with surprising strength. Knowning Seteth as much as she does, Byleth didn't bother to struggle and let him carry her out of the library.

"Ah, thank you Seteth, I didn't see it sneak up here." A revolting stench reached her now canine nose and she began trying to get out of the green haired man's grip and away from it. Tomas came into view, and with a kick of her back legs against Seteth's torso allowed her freedom and she went down the hall back to Jeralt's room, continuing down to the first floor. She heard shouting from behind her but paid no mind.

\---

Her neck was sore but it was worth it to get away from that smell, whatever it was.

She found a corner to rest near the stairs, having no fear towards the soldiers or students. Byleth let them pat her, the physical contact feeling very good for some reason. Thankfully they were soft pats too.

"Oh? I didn't know they let dogs into the buildings."

Byleth's ears perked up, and looked towards the source. Her tail started to move without her input again. Her house leader was coming down the stairs, followed by Lysithea.

"A lot cuter than the other dogs around the monastary. Looks more like a wolf." The young mage spoke. Edelgard nodded her head.

"Probably a hunting dog from a traveling mercenary band, we best keep our distance."

"Then why is it here and not with them?"

"I don't rightly know. Maybe we'd better tell one of our professors, or Seteth."

At his name Byleth reacted with a loud whine.

"*chuckle* Or maybe he's already gotten to him. Remember that loud commotion that had Seteth actually running towards something other than Sylvain going near Flayn?" Lysithea covered her mouth as she giggles.

"Yes, so I guess one of our professors it is...I don't really think Hanneman is up to this though. Our professor is a former mercenary and so could she could better pinpoint who this dog belongs to. Her father could help as well but I don't think he should be bothered with such things." Edelgard looked deep in thought.

"You just want to see Byleth somewhere other than the classroom."

The smell that was currently coming off her house leader was soothing, in a weird way.

"She has much experience with making hard decisions, and I will be the next adrestian emperor, such insight is invaluable to me." The taller girl's voice was quick and sharp to deny Lysithea's words. But Byleth could tell the smell was increasing in intensity.

She quickly got up and trotted over to the two. Much like with Jeralt, she replicated her battle ready stance in dog form. Thinking quickly to the actions she's see the other dogs around the monastary do and those that people have tried to have her replicate, she sticks a paw out to them.

The action makes them both pause.

"Now that's who you should be calling a good girl. Or boy. Can't really...no it's a girl."

Byleth had to mentally pause her tail from breaking off. Being a good girl...meant shake?

A hand took her own, fulfilling the second part of this common dog trick. The white satin glove felt strange, but the smell coming off of Edelgard was pleasant enough to make her not care.

A small smile went across Edelgard's face and Byleth had the sudden urge to lick it.

"I'll leave you to it then. Tell the professor I said hello."

\---

"I guess all we can do is wait for her to return." Edelgard seemed pensive to come into her room, which wasn't surprising. The young woman seemed very private, even to Hubert it seemed. Of course she had so such reservations as it was her own room and confidantly entered the threshold and curled up on her bed.

"You can't lay on the bed, get down." The princess used a firm voice, one that almost had Byleth follow her orders.

Instead she carefully moved her paw to pat at the spot next to her so that Edelgard could sit down, knowing the coming wait will be very long.

The motion didn't seem to work so she tried it again. And again. And again. The princess just stared at her puzzled. Huffing, Byleth scooted over and then motioned with her head what she hoped was the gesture for 'Come here'.

"Are..are you wanting me to sit with you?" Edelgard asked her incredulously, fully aware she was talking to a dog.

Byleth nodded her head and Edelgard finally came over. Seeing her posture was tense, Byleth laid her head on top of her lap to calm her. A hand on her head soon appeared, and without the feeling of a glove covering it. Byleth felt herself being lulled to sleep from the soothing scratches Edelgard was giving her in good places.

Another smell appeared to Byleth. It reminded her of saltwater.

Small somethings seemed to appear on her head, and she risked looking at Edelgard's face.

Tears streamed down her face and it did not feel right. The urge to lick appeared again and Byleth relented to it.

Every inch of her face wasn't safe, regardless of how much resistance Edelgard gave her. And soon there wasn't any, the tears replaced by small giggles.

"You really are a good girl, aren't you?" The princess wrapped her arms around her, and buried her face in her fur, Edelgard's sniffles still present however.

Good girl.

She was a good girl.

To be a good girl meant being good.

\---

Byleth awoke suddenly, and the lack of weird smells and appearance of more colors told her the spell's effect wore off finally. Something shifted right next to her and she quickly realized Edlegard was asleep in her arms.

Carefully extracting herself from Edelgard's arms, she looked at herself to make sure she was back to normal, and sure enough she was. Even her clothes were still in place.

A small cry made her look back to her house leader. Memories of Edlegard's nightmares came to her and she was quick to rush back to her side. Cradling her face, Byleth knew she would be embarassed to wake up in her professor's room.

Taking her coat off, she draped it over Edelgard and gently picked her up. The young woman didn't stir and she started her journey towards her own room. Byleth wondered where Hubert was, knowing he never let Edelgard out of his sight. Ever.

All too quickly she arrived at the princess's room, and she realizes that it'd be difficult to open the door with Edelgard in her arms.

"Oh professor, you made it." The yawning in the sentence told her it was Linhardt. "Let me get that for you. Been fending off Hubert all day. Good night." He opened the door for her and went towards his own room.

Well, that explained where Hubert has been. She made her way inside Edelgard's room, carefully shutting the door behind her with her foot. Walking inside, she let her eyes adjust to the lack of candlelight before moving forward too much. The risk of tripping and harming Edelgard was too much, however small it actually was.

Byleth gently laid her charge on the mattress, and as soon as her hands left Edelgard's body, she stirred a little.

"...the dog..." Was all the sleepy girl could muster.

"Taken care of. Go to sleep." Without thinking, she pat her head in the same manner that she herself has been lavished with all day. Edelgard's eyes closed and she turned to her side, facing Byleth. The professor then reached for her coat, but saw that it was impossible as Edelgard had a tight hold of it.

She sighed as heavily as Linhardt did earlier in the day, before returning to her own chambers.


	2. Part 2 - Crimson Flower

**Summary for the Chapter:**

> Just a normal day during the war. Except it isn't.

Byleth sighed, Ferdinand's jabbering continuing far past the acceptable limit, but their emperor had so far been permitting it so she said nothing. A tap on her shoulder brought her back to the world.

"My teacher?" Edelgard's face had a hint of worry. A glance around showed that the meeting was over, her former students vacating the war room.

Byleth felt her lips curl into a small smile. "My apologizes, your majesty. My thoughts drifted near the end."

"He tends to have that effect. I should be the one apologizing, as we've all become accustomed to it by now, I should of expected it." The emperor covered her hand with her mouth, an attempt at hiding her own smile.

The professor felt her smile widen, having missed moments alone like this with Edelgard. And as if the darkness itself seeked to ruin her day, Hubert was at the emperor's side. "Your majesty, don't forget about your other mee—"

"I have not, Hubert. But thank you for reminding me regardless." Byleth caught the sad look on her face before the emperor's normal stoic facade covered it up. She bowed before she quickly took her own leave from the two, not letting Hubert use her any further against Edelgard during their disagreements.

Byleth swore she could feel two sets of eyes bore into her back, their intent different as night and day.

\---

She was wandering aimlessly around the monastary, without a purpose. The halls that held so many students, now instead were filled with rubble. War was hell, and she knew that very well.

The faces of villagers, family members of those turned victim of bandits and of the more ruthless brigand bands, went through her mind. Especially those that their group were directly responsible for. Jeralt never said why they did it. He just told her where to point her blade. At the time, she didn't even care. It was a job.

But now, she had context. Emotion. Resentment.

How many people died because she never questioned where to point her sword.

"Regretting something?" Her thoughts froze.

The words were of Hubert's usage, but the voice was not.

"Linhardt." She smiled at the green haired mage.

"I must say professor, seeing regret run across your face is a tad strange." He tilted his head in curiosity.

"Memories. From when I was a mercenary."

"Ah, I understand. Well it cannot be helped I guess."

"Hmm." Byleth didn't know what else to say, still not used to being social.

"Oh that reminds me! I never told you about my results, have I?" The mans's voice was excited now. It reminded her of—"My faith spell experiment. That accidentally turned you into a dog?"

Yep, she knew it. "I remember."

"Well I fine tuned it enough that it has nothing but the desired effects. Though I will assume you have no wish for a repeat performace?" It seemed smiles were the topic of the day.

"You assume correctly. It did weird things to my method of thinking for a whole week. Jeralt had a fun time with it though."

"I don't blame you. But you know, I've always wondered—and you don't have to answer, but why did you always refer to your father by his name? I know your living situation was different compared to ours as a mercenary, but I still find it fascinating."

Byleth shrugged. "Everyone else called him Jeralt, or Boss. So I did the same thing."

"Hmm, not what I expected, but at the same time expectable. Well, I'll leave you to your own devices. Why not go to the library in an hour or so?" And with that he walked off with a short wave.

The words were cryptic, but interesting.

\---

An hour later, she found herself looking over stacks of books that had appeared during her five year absence. Sorting them into piles for her own usage, she heard familiar voices.

"—good girl—"

"Again!?"

Byleth slammed the book she had chosen first, her interest gone.

Good girl.

Who was it? Who was the good girl?

She got up and surveyed everywhere around her.

The professor found herself breathing deeply through her nose, hoping to catch a whiff of her quarry, much like a dog would. But the scent tracking of a human is vastly inferior to animals of all kinds, so her instinctual efforts were in vain.

Making her way down the hallway, out of the library, she came across Lysithea. Her mouth refused to let her speak, but it didn't matter. "Oh, hello professor. If you're looking for her Majesty she's probably heading towards her room." 

Edelgard.

Room.

Good girl.

She walked briskly towards said room, Edelgard having taken over Rhea's chambers on the third floor.

\---

The need to get on all fours overwhelmed her, but she pushed passed it, knowing it would actually hinder her speed. Licking her lips to wet them, she realized that the door was right in front of her.

Byleth knocked on the carved oak doors and sure enough, she was there just as Lysithea said.

"My teacher, this is unexpected, but not unwelcome." Byleth knew if she had a tail again it would of broken off by now.

"I need to talk to you." About good girls.

"Of course, though Hub—"

"Alone." Her tone was soft but firm. She looked around the room for his presence but found nothing.

"For once that's a reality." Edelgard smiled, not trying to hide it this time.

"Good. I have an important question to ask you."

"Oh? What is it?"

"I need to know something. Concerning your feelings towards me." Edelgard's face erupted with red, though Byleth had to give her credit for keeping her face straight.

"I—what are you talking about professor?" It started to crack. Then the former mercenary plopped down on all fours. "Am I a good girl?" tilting her head for good measure.

"Linhardt!" The shout was instantanous, but it didn't bother her a bit. She stayed in her doglike sitting position, waiting for her answer.

"Please get up professor. We need to find Linhardt so he can reverse this. I can't believe he used that spell on you." Edelgard grabbed one of her arms to try and pull her up, but Byleth didn't budge.

"Am I a good girl?" Byleth repeated her question.

"Professor, you're under the effects of a spell." The emperor tried again to no avail.

"I'm not a good girl?" An overwhelming feeling came over her and Byleth felt a burning in her eyes, but she could still see it despite the tears, the wavering in the emperor's own.

"Don't...don't tease me like this Byleth." A gloved hand cupped her face. Byleth caught one of her fingers in her mouth, and nipped at it, all while not breaking eye contact.

"Am I..." Byleth sucked hard on the trapped finger, "a good girl?" 

"Byleth...." The former mercenary smiled inwardly as Edelgard moaned. The thoughts created by that single trigger no doubt flooding her emperor's mind.

"El...." She whispered the nickname in response.

"After the war. That's what we agreed on." Edelgard had taken in a deep breath and steadied herself, seemingly destroying the progress Byleth had made. But the professor knew better.

"But I want to know now if I'm a good girl." She had realized that Edelgard never moved her hand, as the finger in her mouth moved deeper inside.

"Then get on the bed." A grin appeared on her emperor's face.

Byleth bounded ontop of it with all fours.

\---

A pleasant soreness greeted her as she woke up, her limbs entertwined with her emperor's.

She snuggled Edelgard tighter, the knowledge that she was a good girl helped her go back to sleep.

\---

"I take it you had a good night's sleep, professor?" A carefree smile was plastered on the man's face.

"...you could say that." The professor was hesitant to reply for obvious reasons.

"Good. Now maybe we can better focus on the war itself."

"You knew?"

"Blind people could see you pining after one another. And I knew about Lady Edelgard's preferred term for Lysithea, and how it could set the side effects of that spell off."

"She was very adamant about you being the root cause of all this. I thought you said you fixed your spell?"

"I did. It's just a black spell now instead of white. I use it to confuse the enemy instead of helping me stay awake. Still within my parameters of success." He kept smiling in his typical nonchalant way. "It never actually wore off on you."

"So I could become a dog again?" She felt her face darken at the thought.

"I don't think so, the effects are strongest in the beginning. The new version just has some mild association with canids, mostly basic commands, while the prototype I used on you was heavily influenced by the dogs around the monastery. Hence the trigger word for you being what it is. Poor Edelgard will have to find a new nickname for our magical powerhouse."

"Linhardt, I need to speak—Ah, Professor!" As if answering a summons, said adrestian emperor walked up behind Linhardt, the scowl on her face quickly morphed into a flustered mess.

"Ah, hello Your Majesty, I was just asking our dear teacher when the wedding would be held. Despite the popularity of summer, might I suggest a transitional season, fall for instance? I feel that change from hot to cold temperatures are the best to reflect your shared duality." The man talked unfazed.

Byleth wanted to hug and slap him at the same time, but her body refused to do either, and instead was doing the weird wheezing noise that Jeralt would make after some fellow would say something amusing. Not quite a laugh, but close to it.

"This is not a joke Linhardt. How could you cast the spell on the professor?! I gave you leave to use it to make the enemy scatter, not brainwash people. What happened last night..."

The former mercenary finally gathered her breath, though she still found the situation amusing. "El, do you remember that dog that you and Lysithea found near the stairs after coming down from the library?"

Edelgard went into thought, and then quickly nodded. "Yes, you...*cough* told me you took care of it."

"I was the dog." She had to bite at her lip to keep her face straight.

"Come again?" The other woman blinked, her purple eyes slowly widening.

"Linhardt used me as his first test subject for that spell. It turned me into a dog for the whole day."

Suffice to say, the only thing not striking crimson on Edelgard was her hair.

"Well, I guess I better tell Dorothea the good news so it'll spread properly." Linhardt made to exit their presence, but her emperor grabbed his hand. "What? Would you prefer spring? Because that's a fine season to have it too."

"That still doesn't explain last night." The emperor's jaw was stiff now.

"She has a stronger reaction to dog related triggerwords. Specifically what you refer to Lysithea as. And please don't say it because it 'will' trigger her again and I really don't wanna see that." He spoke quickly, a wince in his voice.

"El, it's ok. I'm glad it happened." Byleth grabbed onto the offending arm on Linhardt's own, her mere touch letting him free. She intertwined their fingers and brought it to her chest. "Honestly, we probably would of been dancing around it even after we've taken Faerghus and stopped Rhea."

The emperor frown was slowly overcome with another blush. Byleth looked into her eyes, beaming her own smile back. The two gradually embracing one another, without a care towards those that could see them.

A moment later~

"Hey Dorothea, I did it!" Linhardt's voice rang out over the courtyard, making both of them freeze in horror.  
\---

Epilogue

People were unable to utter the words "good girl" when near the empress as the emperor had only so much stamina and free time. But according to Dorothea, a very good friend of the imperial family and a Queen of Brigid, the two embraced the strange quirk rather quickly. Too quickly.

**Notes for the Chapter:**

> Linhardt appeared throughout this whole fic more than I had originally planned, not that I mind as he's almost like a male version of me. The true MVP and an honorary Good Boy(tm).
> 
> I hope the quality from the first chapter carried over, as that tends to happen when I have to quit writing for a day, but I was able to write the majority of these two within a day so here's to hoping.

**Author's Note:**

> I got this idea from Lysithea and Edelgard's supports. I happen to like mild petplay and ship Edeleth hardcore. So naturally this had to happen. Though the petplay doesn't show up til chap 2 and is only mildly implied because I suck at writing and don't trust myself to do it justice.
> 
> There isn't that much detail with descriptors because I tend to get bogged down by it and never finish. Also the Jeralt and Alois bit was not in the original layout but I personally liked it.
> 
> ...Please Tara, please tell me f!Byleth is a good girl too!


End file.
